When a truck, trailer, or some other vehicle is parked at a loading dock, often some type of vehicle restraint is used to keep the truck from inadvertently moving away from an elevated platform of the dock. This allows forklifts and other material handling equipment to safely travel between the dock platform and the truck for the purpose of loading or unloading the truck's cargo.
There are a variety of vehicle restraints available that can be installed at a loading dock for engaging a truck's RIG (Rear Impact Guard), also known as an ICC bar. An ICC bar is a beam that extends horizontally across the rear of a truck, just below the truck bed. Its primary purpose is to prevent an automobile from under-riding the truck in a rear-end collision. However, not all trucks have an ICC bar that can be readily engaged by an ICC-style restraint. In those cases, a wheel restraint might be used for blocking one or more of the truck's wheels.
Perhaps the most common wheel restraint is simply a wheel chock that wedges between the driveway and the underside of the wheel. However, wheel chocks often slip out of position on driveways that are slippery due to oil, rain, ice, sand, gravel, or dirt. Sometimes wheel chocks wedge so tightly under the wheel that they become very difficult to remove. Trucks have also been known to drive completely up and over a wheel chock. Additionally, wheel chocks are often loose items that are not permanently attached to the loading dock area, so they tend to get misplaced.
Some known restraints include powered wheel restraints that travel along a track. However, such wheel restraints cannot always be readily installed at loading docks that might have a drain or some other driveway irregularity situated where the track is to be installed. Moreover, powered wheel restraints are relatively expensive.